Modern inventory systems, such as those in mail-order warehouses, airport luggage systems, and custom-order manufacturing facilities, face significant challenges in responding to requests for inventory items. In inventory systems tasked with responding to large numbers of diverse orders, slow responses to orders may result in an ever-increasing backlog of inventory requests. Furthermore, in inventory systems encompassing substantial amounts of physical space, response times may depend heavily on the location of inventory items and resources to be used in fulfilling a received order. As a result, efficient use of time, space, and system resources can be crucial to successful operation and management of an inventory system.